This invention relates to lasers and more specifically to gas dynamic-transfer chemical lasers using a secondary fuel.
Laser beams and methods for the production of laser beams are well-known as evidenced by U.S. patent application Ser. No. 530,258 of Beckert et al filed Dec. 6, 1974, now U.S. Pat. No. 3,940,298, and U.S. patent application Ser. No. 530,260 of Lee et al filed on even date herewith, both of said applications being incorporated herein by reference.
Gas dynamic and chemical lasers are similar in that both depend upon the competition between stimulated emission and radiationless relaxation processes. Stimulated emission predominates when a population inversion exists between two energy levels.
In chemical lasers, the products of highly energetic chemical reactions are formed directly in vibrationally or electronically excited states with the upper levels preferentially populated, whereas in gas dynamic lasers, an initially hot gas in thermodynamic equilibrium is rapidly expanded through a supersonic nozzle, and inversion occurs by differential relaxation processes in the nonequilibrium nozzle flow.
One of the best gas dynamic lasers expands a gas of 89% N.sub.2, 10% CO.sub.2, 1% H.sub.2 O. This gas has the disadvantage of being virtually impossible to generate by the combustion of non-gaseous fuels and oxidizers. At the present time, most GDL systems depend upon bottle or cryogenic gases, which require complicated valve systems along with other complicated and bulky equipment.
Recently, continuous wave operation of 10.6 in HCl--CO.sub.2, HBr--CO.sub.2, DF--CO.sub.2 chemical lasers has been described. The laser emission is believed to be the result of upper CO.sub.2 laser level pumped by vibrational-rotational energy transferred from excited HCl, HBr, DF and HF molecules formed by chemical reactions.
In the DF--CO.sub.2 system, F. (provided by partial dissociaton of F.sub.2 by photolysis, thermolysis, reaction of F.sub.2 with NO. or thermal dissociation of SF.sub.6 or NF.sub.3) is mixed with CO.sub.2, N.sub.2 and D.sub.2. The rapid and efficient chain reactions, F. + D.sub.2 .fwdarw. DF* + D. and D. + F.sub.2 .fwdarw. DF* + F. are driven to completion as the mixture flows along a Teflon reaction tube. The present chemical laser systems have a disadvantage in that generation of halogen radicals by thermolysis or photolysis requires the addition of extra equipment such as furnaces or flash lamps.
A further problem of the gas dynamic chemical transfer laser is that the number of population is tied to the Boltzman distribution fraction of excited molecules. If this fraction could be increased the laser effect would be more marked and effective. Present systems, however, do not permit this increase.